Alternating-current motor.



0. LE G. FORTESGUE.

ALTERNATING CURRENT MOTOR.

APPLICATION FILED 113.21, 1911.

' Patented Dec.30,1913.

ENTOR m a iazwi,

. AT TURNEY Y UNITED swarms PATENT creme.

CHARLES LE e. ronrnscnn, or rrrrsnunsn, PENNSYLVANIA, ASSIGNOR T emINGHOUSE ELECTRIC AND manuraoruame COMPANY, A CORPORATION- or PENN-rent. The auxiliary transformer is relacontrol and regulation of singlephase altersteps in the regulation. of the motor.

ergy is supplied from any suitable source SYLVANIA.

0 ALTERNATING-CURRENT MOTOR.

Application filed February 21,1911. serial Ne. 609,340.

To all whom it may concern Be it known that 1, CHARLES L11 G. For.-TESCUE, a subject of the King of Great Britain, and a resident ofPittsburgh, in the county of Allegheny-and State of Pennsylvania, haveinvented a new and useful improvement in Alternating-Current Motors, ofwhich the following is a specification.

My invention relates to dynamo-electric machines and it has specialreference to the nating current motors of the commutator type.

. The object of my invention is to provide means for varying the speedand characteristics of motors of the class above indicated in a simpleand inexpensive manner without material loss of energy.

Single phase series-connected alternating current motors of thecommutator type have been extensively utilized for railway work and thevoltage applied to the terminals of the motor in starting has usuallybeen varied by means of a large number of taps on a main transformerwhich is energized from the relatively high-potential line conductor.

My invention is not intended to replace the main transformer or othervoltage-regulating means,.but permits a very gradual acceleration andacareful regulation to be effected with a very few taps on the maintransformer.

According to my present invention, I so associate an auxiliarytransformer with the motor as to permit a relative adjustment betweenthe armature current and the field curtively small-and inexpensive andis provided with a number of taps representing small In starting themotor, the auxiliary transformer may be regulated over its completerange between. successive steps in the reguiation of the maintransformer.

Figure of the accompanying drawing is a diagrammatic view showing thearrangement'and circuit connections of a system embodyingmy invention,and Figs. 2 and 3 are similar views showing modifications ofmyinvention.

Referring to Fig. 1 of the drawings, en-

(not shown) through line conductor 1, trolley 2 and conductor 3 to atransformer the opposite terminal of the transformer Patented Dec. 30,1913;

being connected to ground or to a return] be engaged successively by anarm 16, said arm being connected to the conductor 10. The taps 9 on themain transformer are relatively few and quite widely separated, whilethe taps 14 on the transformer 13 are close together and are quitenumerous,"the a1- rangement of parts being such that a very gradualacceleration or retardation ofthe motor may be effected by adjusting thearm 16 over its entire range for each voltage step as affected by anadjustment of the arm 7.

\Vhile I have shown a single motor for the sake of simplicity inillustration, it will, of course, be understood that two or more atransformer winding 13 hav-.

motors will usually be employed and that the capacity of the transformer4: will be very much greater than that of the transformer 13. It willalso be understood that it is very much less expensive to provide thesmalllow-voltage transformer 13 with a large number of taps and thetransformer 4 with ,a small number of taps than to supply the largehigh-voltage transformer with a large numberof taps.

It is evident that the current-in the path through the armature windingand the current in the path through the field magnet winding will eachbe approximately inversely proportional to the turns of the transformerwinding 13 which are included in the same branch and consequently byproperly setting the arm 16 during the normal operation of the motor,the characteristics of the motor maybe materially altered.

For example, the flow of current may be largely increased withoutabnormally increasing the armature current. Inother words, the currenttraversing the field Winding maybe varied relative tothe currenttraversing the armature winding and this adjustment maybe utilized notonly for effecting a gradual acceleration of the motor.

T l ig. 2 oil? the drawings, the transformer is alaccd by a two-windingtransformer having a primary Winding 17 and a second ary abiding 1S, anda transformer winding 13 is replaced by a whirling 19 to the middlepoint oi? which one terminal of 'u'indiug 152 and the conductor 10 arepermanently connected. The armature 1}. peri'iiuinently connected to oneend of the windlll and the free tcri'ninal of the Winding is connectedto a point near the opposite end of i contact arm 20, which engages anyone of a plurality of contact terminals for the res iective lay s Fill.Substantially the same lotion is effected by the arn'i 20 as that ted bythe arm 16 of Fig. 1.

ii ig. 3 the trausii'ornler winding 19 of 4 is replaced by windings andwinding 2:2 being connected in circuit cell the conductor and oneterminal 1* ari'i'iature 11., and the other terminal ie armature beingconnected to the conor (ii ()ne terminal of the field winding 1'connected to the junction of the arniall and the windings and 2 and alsoearth, and the opposite terminal of the f" ,id winding is connected toanyone of eral points in the winding through the biting arm 20 and taps21. The arm 20. figure, eliects the same regulation as the other figuresthat the scope of my invention l desire shall only be limited by theappended claims.

ii claim as my invention: L The combination with an alteri'iatingcurrent motor having its armature and field the field the transforn'icrwindin through a i l i l l l l g l l 1 magnet windings connected inmultiple circuit, of means for varying the relative c111 rentstraversing the respective branches of said circuit, said meanscomprising means for varying the relative inductance of said branches.

2., The combination with alternating current motor having an armatureand field magnet windings connected in multiple circuit, of atransformer winding, a portion of which is connected '11 one branch ofthe motor circuit and a second portion of which is connected in theother branch of the motor circuit.

3. The combination with an alternating current motor having armature andfield magnet windings connected in. multiple, circuit, of externaladjustable means for maintaining a desired relation between the currentsin armature and field magnet Windings and comprising a dividedtransformer winding having its parts respectively connected in the fieldand arnlature branches of the motor circuit.

4:. The combination with an alternating current motor having arn'iatureand field magnet windings and a conu'mitator, and a source of current,of a regulating transformer which is connected between the armature andfield magnet windings of the motor, one terminal of said source beingconnected to an intermediate point in said regulating transformer andthe other terminal of said source being connected to the remainingterminals of the ari'nature and field windings] 1n testimony whereof, Ihave hereunto subscribed my name this 13th day ol Feb. 1911..

CHAR ES LE Witnesses:

' R. J. DEARBORN,

B. B. Hines.

